Resistant integrated keypad and a method for making the same

ABSTRACT

This invention relates to keypads with push buttons and in particular to integrating different parts of a keypad to provide better and more secure functioning.  
     The keypad according to present invention is characterized in that it comprises a first component including a cover portion and a key portion forming together a single structural entity, said structural entity allowing the key portion to move within a limited range in relation to the cover portion; and a substantially soft second component attached to the first component for covering space between the cover portion and the key portion of the first component and making composed compound construction substantially tight, still allowing the limited movement of the key portion of the first component.

TECHNICAL FIELD

[0001] This invention relates to keypads with push buttons and inparticular to integrating different parts of a keypad to provide betterand more secure functioning.

BACKGROUND OF THE INVENTION

[0002] The known keypads in portable electronic devices comprise a coverportion and different key portions. These two separate parts are locatedso that the key portion comes through the cover portion. The keytops,which are situated outward from the cover, move into an inward directionwith respect to the cover when pressed. This provides tactile feedbackto user. Another important thing for the user is that each key isidentified by printing some markings or characters on the outer surfaceof a key or by embossing the flexible cover to create raised areas at oraround the keytop locations.

[0003]FIG. 1a is a sectional exploded view, which illustrates a knownstructure of a keypad. These kinds of keypads are used for example inmobile telephones and personal digital assistants. The upper surface ofa printed circuit board 101 comprises a number of contact areas, whereat least two conductive strips 102 and 103 come close to each other.Supported over the printed circuit board 101 and separated from it by aperforated insulation layer 104 is an array of conductive domes 105 sothat each conductive dome 105 lies directly above the conductive strips102 and 103. Key mat 106 is located on top of the conductive domes. Itis made of an elastic material. A bulging protrusion 107 of the key matprotrudes slightly out through the holes in the outer cover 108. In somekeypads hard key-specific parts are used above the bulging protrusions107 to provide a harder tactile feeling for the user (not shown in FIG.1). FIG. 1b shows the same structure in assembled configuration.

[0004] A cover portion 108 is the outer part of the structure in FIGS.1a and 1 b. In these figures the key mat 106 and the bulging protrusions107 form a key portion. The rest of the structure, a printed circuitboard 101, conductive strips 102, 103, a perforated insulation layer 104and conductive domes 105 form the actual electrically functioning partof the keyboard.

[0005] One problem with prior art keypad is printing desired markings orcharacters on the surface of each key. Such printing operation should beperformed directly on the surface of the each individual key or button.These buttons have substantially cubic configuration. This kind ofprinting operation is complex and less efficient compared to theprinting operation in which a marking or the like is directly printed ona sheet. It is also difficult to perform a fine printing. Also it isnoted that, when a plurality of keys are simultaneously printed with amarking, misregistration between the keytops and a printing means wouldoccur, since the keytop plate has flexibility. As a result, simultaneousprinting of a marking or the like on number of keytops is impossible.This reduces the efficiency of the printing operation.

[0006] Another unsolved problem of the prior art solutions raises fromthe fact that there must be an interstice between the key portion andthe cover portion for the keytop to be able to move. The final productshould be as compact as possible, so the interstice between the keyportion and the cover portion should be kept small. Advantageously thisinterstice should be smaller than 0.5 mm. On the other hand in the mouldthere must be accomplished a closing surface to the interstice. Thisprovides that the cover should be thicker than 0.5 mm.

[0007] In the publication U.S. Pat. No. 6,064,019 there has beenintroduced a resilient switch cover and an actuator button compactlyinstalled through the aperture in the cover. Compactness of the solutionof this patent is based on the size of the button, which is larger indiameter than a corresponding diameter of the aperture in the cover.

[0008] In the publication U.S. Pat. No. 6,023,033 there has beendescribed a method for producing a keytop plate. In this solution thekeytops are formed by moulding a resin at the predetermined positions ofa synthetic resin film. A moulded elastomer plate is attached to formedkeytops. The waterproofing capability of this construction is based onthe fact that in the area of the moulded elastomer plate, other than theareas to which the keytops are attached, there are no through-holes.

[0009] It is also known by the prior art to isolate a separate key bysome soft substance. All prior art solutions are generated with numberof separate manufacturing steps, which often require number of differentmoulds and intermediate storages. These different production steps areusually expensive and inefficient.

SUMMARY OF THE INVENTION

[0010] The object of the present invention is to overcome the drawbacksof the prior art. A further object of the present invention is tosimplify the manufacturing and to produce a compact keypad resistantagainst harmful environmental effects.

[0011] The objects of the invention are achieved by integrating the keyportion to the cover portion. This new configuration packs the keys andthe cover to one solid and essentially rigid portion, which ismanufactured in a limited number of steps. Further a soft component isattached to the rigid component to make the construction resistantagainst harmful environmental effects.

[0012] The invention is directed towards the features of the keypad,which are described in the independent claims. According to the presentinvention the keypad is characterized in that it comprises a firstcomponent including a cover portion and a key portion that form togethera single structural entity so that said structural entity allows the keyportion to move within a limited range in relation to the cover portion;and a substantially soft second component, which is attached to thefirst component for covering space between the cover portion and the keyportion of the first component and making composed compound constructionsubstantially tight, still allowing the limited movement of the keyportion of the first component.

[0013] According to the present invention there is produced a rigidcomponent, which includes a cover portion and a key portion, and a softcomponent, which makes the configuration tight. The different structuresin the rigid component are generated by components having certainmechanical characters. For example in fixed, hard parts there is simplya thicker material layer while in flexible parts a thin layer is used.Also in the mechanical construction different shapes are used knowingthe fact that planar structures can be used in flexible parts of thecomponent, whereas for the hard, rigid parts for example a cubic-like ordome structure would be more appropriate. The soft component is attachedto the rigid component either mechanically or chemically.

[0014] The new compact construction introduced in the present inventionis easier and cheaper to manufacture, because the rigid component can bemoulded in one mould. The whole structure can be generated with aconventional mould without any moving parts. This has the furtheradvantage that also the manufacturing process is stable, so it includesless variables and can be carried out effectively.

[0015] In the keypad structure of the present invention, there is acertain interstice between the keytop and the cover, although theseparts are made as one rigid component.

[0016] The soft component covers the interstice and makes the structurecompact. The soft component so prevents dirt and dust from penetratinginside the structure, as dirt and dust might otherwise cause a key tostick or not to function properly. All these kind of problems are solvedby the present invention. Also with the proper choice of the materialsand substrates water resistance may be achieved.

[0017] The tactile characteristics of this new construction make the useof the product comfortable. If the whole keypad would be made offlexible material, the tactile feeling and feedback would remainrelatively soft. A hard tactile feeling, which is preferable to mostusers, may be provided by a moulded construction introduced here. With aharder tactile feeling the user can be more secure about her/hisselections. The more the depth-directional movement is needed, the morethere must be space surrounding the moving parts either in vertical orhorizontal direction.

[0018] The graphics or, in the other words, printing markings andcharacters on the pushbuttons, may be carried out easily with this newconstruction presented in this invention. Now graphics can beimplemented even in the mould, and/or printing operations can either bedone straight on the key made of rigid component or to the softcomponent area.

BRIEF DESCRIPTION OF DRAWINGS

[0019] The present invention is described in detail with theaccompanying drawings.

[0020]FIG. 1a illustrates a known keypad structure in exploded view,

[0021]FIG. 1b illustrates the keypad structure of FIG. 1a in assembledconfiguration,

[0022]FIG. 2a illustrates the embodiment of the present invention, wherethe rigid component is seen from a side,

[0023]FIG. 2b illustrates the embodiment of the present invention, wherethe rigid component is seen from the overhead view,

[0024]FIG. 2c illustrates the embodiment of the present invention, wherethe soft component is seen from a side,

[0025]FIG. 2d illustrates the embodiment of the present invention, wherethe soft component is seen from the overhead view,

[0026]FIG. 3 illustrates a moulded keypad with number of keys accordingto one advantageous embodiment of the invention,

[0027]FIG. 4a illustrates a moulded keypad and attachment of the softcomponent according to advantageous embodiment of the invention, and

[0028]FIG. 4b illustrates a moulded keypad and attachment of the softcomponent according to other advantageous embodiment of the invention.

DETAILED DESCRIPTION OF THE INVENTION

[0029] In the following description of the various embodiments,reference is made to the accompanying drawings, which form a parthereof, and in which is shown by way of illustration various embodimentsin which the invention may be practiced. It is to be understood thatother embodiments may be utilized, and structural and functionalmodifications may be made without departing from the scope of thepresent invention.

[0030]FIG. 2a is a cross-sectional side view of a certain part of akeypad, which constitutes, according to the present invention, theso-called rigid component. In FIG. 2a the key 204 is attached to thecover portion 201. The protrusion 203 illustrates a graphic or somemark, which is to be on the final surface plane after a certain softcomponent has been injected as will be described later with theaccompanying FIG. 2c. A groove 202 is advantageous, if the softcomponent is to be attached mechanically to the rigid component, sincewith a groove 202 the mechanical joint can be made compact, but stilldemountable. The attaching soft component has a counterpart, which fitstight to the groove 202, because of the elasticity and a shape of thesoft part. The same effect may be illustrated so that, instead thegrooves, the rigid component has protrusions and the soft component hasholes with smaller diameter than protrusions aligned with them. FIG. 2bshows the same one-component structure from the overhead view. There isthe groove for the mechanical connection 202, the key, or the pushbutton204 and the protrusion 203, which in this exemplary embodiment, as canbe seen from the FIG. 2b, is a graphical arrow.

[0031]FIG. 2c illustrates the corresponding keypad after the softcomponent has been injected. In FIG. 2c the basic structure is the sameas described in the previous FIG. 2a. Made of rigid component there is acover portion 201, groove 202 for a mechanical joint, protrusion 203,which implements graphics and finally the key 204. The soft component205 is injected on the top of the rigid component structure. The softcomponent 205 binds the pieces of the rigid component to one compactconstruction. Also the soft component 205 makes the surface of theconstruction flat still enabling the movement of the keys. This softcomponent structure is seen from the overhead view in FIG. 2d. As can beseen in FIG. 2c the upper surface is now substantially flat. Only thekeys 204 protrude upwards from the surface. The graphics 203 are at thesame level as the injected soft component surface 205. The possiblegroove 202 is also filled with the soft component.

[0032] In this application the two used components are named as rigidcomponent and soft component. The term rigid component is used in thisapplication to convey that the material is substantially hard, or in asubstantially hard form. So the selected material is to be fast andsolid. This means that in parts where no specifically provided,relatively thin and elongated portions exist, the rigid component itselfdoes not bend. Limited elasticity can still be achieved by designing themechanical construction of the component to include certain relativelythin and elongated portions. So small movements are allowed even if thecomponent is called rigid. The term soft component is used in thisapplication to convey that the material is substantially flexible andelastic, or in a substantially flexible or elastic form. This softcomponent covers unwanted gaps tightly and conforms to a movement of thesurrounding parts. These features maintain the construction compact andresistant against harmful environmental effects.

[0033] When a hard tactile feeling is desired feature, the keytopsshould be made of some hard component. Also it is advantageous that theprotective cover portion is made of rigid material. According to thepresent invention, the keytops and the cover portion are made of a sameselected substrate at the same time. In this application this selectedmaterial or substrate is generally called the rigid component. Thisrigid component could be for example acrylonitrilebutadienestyrene,polycarbonate, polypropylene, polystyrene, hard polyethylene, polyvinylchloride or some other applicable plastic. Choice of the material alsomakes some requirements to the structure. The key material is selectedto be rigid, which means, that there must be some elastic, flexible,non-rigid parts in the construction to able the keytop to move towardsthe cover portion. This requirement can be fulfilled with the relativelythin and elongated part 206 of the structure that connects the keytopportion to the cover portion. In some prior art solutions a spring isused to produce this elastic connection. According to present inventionthis is not possible, since the whole integrated keytop-cover-portion isto be made by one manufacturing step. Thus all parts included in thisintegrated construction are produced of the selected rigid component.

[0034] A keypad with several keys (or push-buttons) is introduced inFIG. 3. According to this one advantageous embodiment of the presentinvention keys 301, made of rigid component, are movable, even if thekeys themselves are rigid. This is implemented so, that every key hasone fastening element 303, which in this embodiment is called the leg,which connects the key portion to the cover portion. This leg is eithermoulded at the same time and made of the same material as the combinedkey-cover portion or manufactured separately so that in the assembledconfiguration it is attached to the corresponding key portion and thecover portion. It is also possible to manufacture legged key portionsthat are attached to the cover portion at the distant end of the leg.This leg is thin and planar, so its mechanical properties make itflexible. This kind of leg-structure is advantageous in keypads, whichhave number of keys, because this kind of construction enables themoulding to be done without any moving parts. As a consequence thenumber of manufacture steps is minimized and keypad can be producedeffectively. After this first key-leg-cover-part is moulded orassembled, according to the invention, the second moulding with softcomponent is to be done.

[0035] The soft component is used to fill the circular gap around thekey portion 302. This enables the key 301 (or button) to be pushed downfor some action. When the gap around the key portion 302 is filled withsoft material, it bends elastically with the movement of the key. Alsothis moving of the key 301 causes the wanted tactile feedback to theuser. The soft component is then attached around the key portion 301 ofthe previously moulded piece. This soft component might be for examplesilicone rubber, soft polyethylene, soft polyamide or some thermoplasticelastomer (TPE). The thermoplastic elastomers are soft, flexible andcommonly used instead of usual plastic for injection moulding andextrusion of soft flexible applications.

[0036] The key portion and the cover portion are not necessarilyconnected to each other at all. With different nozzles, keys may beinjected so that they will not be in touch to each other or to the coverportion. In this embodiment of the present invention, the keys are kindof separate enclaves, until the soft component is injected. So the keyportion, the cover portion and the soft component may all be fabricatedby one mould, step by step, without any storage or handling in between.Also this minimizes the assembly steps of the production.

[0037] According to one advantageous embodiment of the present inventionboth rigid and soft component materials can be chosen to be polyamide 12(PA12). Polyamide 12 can be used in a hard, rigid form and also in asoft, flexible form. This enables the both, rigid and soft components,to be produced of the same material. This is advantageous, because thesematerials fit together, so these are compatible. Also if the product isrecycled afterwards, there is no need to separate these parts from eachother. The rigid component is made, according to this advantageousembodiment, of polyamide 12 hard phase. For the soft component the samepolyamide 12 is used as its soft phase. The soft component, here softpolyamide 12, is attached to the rigid component construction. Attachingof this soft component is described in the following in detail with theFIGS. 4a and 4 b.

[0038]FIGS. 4a and 4 b are examples of the possible implementations forattaching the soft component 404. In both figures the rigid componentkey structures are equal, including a keytop 401, a cover portion 403 aswell as a fastening element 402, which combines the keytops 401 to thecover portion 403. The first integrated part is made in onemanufacturing step, moulding the keys 401, cover 403 and the combiningelements 402 all at the same time. According to one embodiment of thepresent invention, illustrated in FIG. 4a, the soft component 404 isattached to the upper side of the structure. This has the advantage,that some marks or characters can be printed on this area, either on topof the soft component or beneath it if the soft component is transparentor translucent. This enlarges the printing area, which leads to theelaborated and individualized marking of keys. The whole soft componentarea can be used to mark keys and add further graphics.

[0039] In FIG. 4b the soft component 404 is attached on the underside ofthe structure. The soft component is attached to the rigid componentstructure by pressing, moulding or injecting. Further the connection canbe mechanical or chemical. Chemical connection is more resistant. Forexample if water resistance is required, the connection must bechemical. Although in many cases it is enough to have dustor moistureresist keypad, in which the mechanical connection can be used. Also ifused materials are to be separated later for example for the recycling,the mechanical connection enables later separation of the components.

[0040] A cutless and compact keypad is advantageous especially, when thekeypad is used and situated on table or on some other plane. Situationslike this are the most likely to suffer from moisture and dirt or dust,which either impairs the functioning of the key or makes it unable tofunction.

[0041] According the present invention, only a key portion and a coverportion of a keypad are modified. The structure consisting of the rigidand soft components described above can be used to replace the knownparts 106, 107 and 108 illustrated in FIG. 1. The invention does notconcern any of the electrical functions behind the key-cover-portionpresented in this application. The keypad might consist of an electricalswitch or any other known construction and situation behind thekey-cover-portion.

1. A keypad comprising a first component including a cover portion and akey portion forming together a single structural entity, said structuralentity allowing the key portion to move within a limited range inrelation to the cover portion; and a substantially soft second componentattached to the first component for covering space between the coverportion and the key portion of the first component and making composedcompound construction substantially tight, still allowing the limitedmovement of the key portion of the first component.
 2. A keypadaccording to claim 1, wherein the first component is rigid.
 3. A keypadaccording to claim 1, wherein the second component is on a keytop sideof the construction made of the first component.
 4. A keypad accordingto claim 1, wherein the second component is on a keybottom side of theconstruction made of the first component.
 5. A keypad according to claim1, wherein the first component is made of material, which is one of thefollowing: acrylonitrilebutadienestyrene, polycarbonate, polypropylene,polystyrene, polyethylene, polyvinyl chloride, polyamide 12; and thesecond component is made of material, which is one of the following:silicone rubber, polyethylene, polyamide, thermoplastic elastomer,polyamide
 12. 6. A keypad according to claim 1, wherein the limitedmovement of the key portion is enabled by coupling the key portion andthe cover portion by a handle, which is reversibly bendable for its formand characteristics.
 7. A keypad according to claim 1, wherein on thatsurface of the first component, which is essentially covered by thesecond component, there is a wrought protrusion essentially as thick asthe second component, so that the protrusion reaches through the secondcomponent to the surface, which is intended for the use of a user.
 8. Akeypad according to claim 1, wherein the connection between the firstand the second component is mechanical.
 9. A keypad according to claim1, wherein the connection between the first and the second component ischemical.
 10. A method for making a keypad, comprising the steps of:moulding a first component including a cover portion and a key portion,said cover portion and key portion forming a single structural entity,wherein said key portion is arranged to move limitedly in relation tosaid cover portion; and attaching a substantially soft second componentto the first component to cover a move-enabling space between said coverportion and key portion of the first component to make composed compoundconstruction substantially tight.
 11. A method according to claim 10,wherein the step of moulding the first component and the step ofattaching the second component are sequential steps and both steps aremade with the one and the same mould.
 12. A method according to claim10, wherein the second component is attached to the construction made ofthe first component by moulding.
 13. A method according to claim 10,wherein the second component is attached to the construction made of thefirst component by injecting.
 14. A method according to claim 10,wherein the second component is attached to the construction made of thefirst component by pressing.
 15. A method according to claim 10, whereinthe second component is attached on a keytop side of the constructionmade of the first component.
 16. A method according to claim 10, whereinthe second component is attached on a keybottom side of the constructionmade of the first component.
 17. A method according to claim 10, whereinthe components are coupled mechanically to each other.
 18. A methodaccording to claim 10, wherein the components are coupled chemically toeach other.